In most semiconductor manufacturing techniques, a number of individual electronic packages, such as semiconductor Chip Scale Packages (CSP) are formed on a single substrate. These individual packages have to be singulated or separated before use. One method of substrate singulation is to use a dicing saw to cut the substrate when it is mounted on a cutting chuck. Each substrate typically consists of either an array of integrated circuit devices or sections of multiple arrays called panels. These panels may be arranged in groups of three to five that are equally spaced along the length of the substrate. The dicing process produces arrays of sawn or singulated electronic packages which need to undergo further cleaning, rinsing and drying processes. The said processes should preserve the relative positions and orientations of these singulated packages and must not cause packages to tilt and overlap in order not to create handling difficulties during subsequent processes along an assembly line.
One way of cleaning and drying singulated substrate is by the use of a pressurized water nozzle and air blower wherein the singulated substrate is mounted on a holding nest and covered with porous material. However, such pressure-rinse nozzle cleaning causes difficulties in humidity control, thus incurring overheads in drying time of the singulated substrate and may affect the circuitry of the equipment. Furthermore, it necessitates complicated design and fabrication of tools for holding the substrate in position within a pressurized chamber to carry out rinsing. Another way is to use an ultrasonic tank, wherein the singulated substrate is mounted on a nesting structure, covered, and is immersed in an ultrasonic cleaning liquid. However, the set-up of the said ultrasonic tank is complicated and usually results in longer processing time, longer drying time and difficulties in contamination management of the ultrasonic cleaning liquid. In addition, the driving frequency of such a conventional ultrasonic tank may not be appropriate for cleaning the wire bonded electronic devices. A third way is to use centrifugal cleaning. A singulated substrate is held on a carrier by means of vacuum. The carrier then spins quickly and the substrate is rinsed by pressurized water nozzles and then dried by the spinning motion. However, water and debris will diffuse through the gaps in the singulated substrate and be trapped underneath the substrate due to the vacuum force of the carrier. Eventually, watermarks and contamination are formed on surfaces of the singulated substrate.
There is a need for an improved process to clean the singulated substrate down to submicron levels and to shorten the cycle time for the entire cleaning process.